It is apparent that blood and intravenous solution bags made from polyvinyl chloride (hereinafter referred to as "PVC") have all but completely superseded glass containers in delivery of blood and/or intravenous solutions to humans or animals. However, there is still a great deal of dissatisfaction with PVC bags because large amounts of DOP plasticizers and vinyl chloride monomers leach and/or hydrolyze into the blood and/or intravenous solutions contained in PVC bags and ultimately find their way into humans and animals being treated. Therefore, a great deal of research has been conducted in attempts to develop new plastics which can be used to make blood and intravenous solution bags and which will not hydrolyze and/or leach into blood or intravenous solutions.
A material for use in making blood and intravenous solution bags should have the following properties:
(1) It should be clear (preferably, transparent); PA1 (2) it should be able to withstand autoclaving at 240.degree. F. to 270.degree. F. PA1 (3) it should be suitable for film-forming and/or extrusion; PA1 (4) it should be fairly soft to the hand; PA1 (5) it should be capable of withstanding a drop of six feet when full; PA1 (6) it should be suitable for heat sealing; PA1 (7) it should have a price which is not prohibitive (preferably, under $2/pound); and PA1 (8) it should not hydrolyze and/or leach into blood or intravenous solutions.
PVC passes all of the above tests except #8, which is probably the most important one and which is why the medical profession is still not happy with present-day PVC bags. As far as other commercially available materials are concerned, test #2 eliminates all available materials except Mylar, nylon, polycarbonates, polysulfones, some polyurethanes, some silicones, cellulose, cellulose triacetate, fluorinated ethylene, polytetrafluoroethylene, polyfluorochloroethylene and polyvinyl alcohol. Mylar is unacceptably stiff when more than a mil or two thick; it is unacceptably weak unless it is considerably thicker than that, and it cannot be heat-sealed properly. (Bar heat sealing is possible, but the required temperatures are such that the material immediately next to the heat seal is annealed, and bags formed from bar heat sealed Mylar accordingly do not have the required strengths). Inability to obtain leak-proof heat sealing eliminates cellulose, cellulose triacetate and polytetrafluoroethylene. High water absorption and permeation eliminates nylons, polycarbonates and polyvinyl alcohols. Price, as well as other deficiencies, such as stiffness, lack of clarity, and inability to obtain leak-proof heat sealing, eliminates fluoronated ethylene, polyfluorochloroethylene and polysulfones.
Probably the most promising candidates known heretofore for replacing PVC in blood and intravenous solution bags are some of the silicones and polyurethanes. They are soft, have a good hand feel, are clear, and some of them can withstand temperatures of up to 250.degree. F. Unfortunately, all of these materials hydrolyze, producing unwanted chemicals such as amines and esters. In addition, the commercially available polyurethanes and silicones are either not heat sealable or not autoclavable.